The present invention relates generally to a process for producing decorative frosted glass articles, and more particularly to a process for printing images and lettering on frosted glass to remove the effects of frosting, so that the printed areas appear transparent to light.
In the manufacture of decorative glass and decorative glass articles, it is often desirable for the glass to have a frosted appearance. This frosted-glass effect is produced by roughening the surface of the glass, so that light passing through the surface becomes highly diffused. Frosted glass provides an aesthetically pleasing appearance due to its optically translucent quality, which transmits light but prevents the perception of distinct images. Because of the aesthetic quality of frosted glass, it is used in a wide range of glass articles of manufacture including glass panels, bottles, glassware, lighting fixtures, plaques, and decorative ornaments.
It is often further desirable to frost the surface of the glass article selectively, so that most of the glass surface has a frosting effect while some portions of the glass surface remain clear and transparent to light. In the manufacture of some glass bottles, for example, the entire surface of the bottle may be frosted except for designs, brand names, company logos, or other lettering, which remain unfrosted and clear. The effect produced by a transparent design or transparent lettering in a field of translucent frosted glass is aesthetically pleasing to the eye, and several manufacturers have adopted this technique for their products.
There are several commonly known methods for producing selectively frosted glass articles, such as abrasive blasting, acid frosting, and laser etching.
In the method of selective abrasive blasting, a stencil of the desired design or lettering is first produced using brass, steel, or a resilient material, such as rubber or vinyl. The stencil is brought into contact or otherwise aligned with the glass article in the position where the design or lettering is to be registered on the glass. The entire glass article is then abrasive blasted. In abrasive blasting, particulate material such as aluminum oxide grit is mixed with air and directed under high pressure to the glass surface, producing a roughening or abrading of the glass surface in all areas not covered by the stencil. The areas covered by the stencil remain clear and transparent.
Although this method is basically effective, there are several disadvantages. The process is slow and costly. Positioning and removing the stencils is a manual operation that requires a high skill level to achieve acceptable or uniform results. Also, the stencils are subjected to the sandblasting effects, reducing the usable life of the stencil. As the stencil degrades there is a corresponding loss of uniformity between glass articles being produced. Furthermore, because the stencil must have sufficient thickness to resist the effects of abrasive blasting, fine details in designs and lettering cannot be obtained. Abrasive blasting using rubber or vinyl is not suitable for high volume production of selectively frosted glass articles.
In the method known as acid frosting, an organic acid resist mask is deposited by screen printing or other means on the surface of the glass article in the desired design or lettering pattern. The acid resist mask is completely dried, and then the glass article is immersed in an acid bath. An acid such as hydrofluoric acid roughens the glass surface to achieve the frosting effect. The portion of the glass surface not covered with the acid resist mask will receive the frosted effect; the portion of the surface covered by the acid resist mask will remain clear. The glass article is then rinsed and the acid resist mask is removed by any of a number of known methods. In one method, the glass surface is soaked in a hot solvent to soften the mask material, and the surface is then rinsed with detergent until all the mask material is removed.
Although this method of selectively frosting glass achieves generally good results, the method has several disadvantages. The process requires heated screens for depositing the acid resist mask on the glass article. Therefore, precise temperature control must be maintained throughout the entire process. Also, the process is slow because it requires a period of drying before the next step in the operation can be performed. Finally, the removal of the mask material after the frosting process is time consuming and expensive. This is due to the use of hot solvents and the stage of rinsing with detergents, which may need be repeated until all of the mask material is removed.
Another known method for producing selective frosting of glass is laser etching. In laser etching, a computer controlled laser beam, guided by a graphics drawing and layout program, scans across the surface of the glass article and etches the desired design or lettering into the surface of the glass article. The burning off of the surface layer of the glass gives the design or lettering a frosted appearance. To achieve the effect where the whole glass article is frosted with only the desired design or lettering remaining clear, the laser beam, under computer control, scans and etches the entire surface of the glass article except for the area of the design or lettering.
Using laser etching to achieve selective frosting of glass has the disadvantage of requiring expensive specialized equipment. Also, when the majority of the surface is to be frosted, laser etching is a very slow and time-consuming process, because the entire surface of the glass article must be scanned by the laser. The number of finished glass articles produced per unit time is small and the process is not suitable for volume production.
There exists a need for a method of producing the same desired effect of selective frosting of glass without the drawbacks present in the prior art. There is a need for a method of achieving the effect of selective frosting of glass which is also cost-effective and reliable and which can be practiced with a minimum of specialized expensive equipment and specialized preparations and techniques. The present invention overcomes the disadvantages of the prior art.
A solution to the problems of prior methods of selectively frosting glass is provided in the glass printing process of the present invention, which uses screen printing technology to cancel out or remove the effects of frosting from a glass substrate or from a manufactured glass article in a selected pattern.
The present invention is useful for creating any type of visible pattern on frosted glass including images, letterings, logos, and designs, giving the appearance of selective frosting of the glass article. Furthermore, the effect of the present invention is achieved in a reliable, cost-effective manner, which can be accomplished without the highly specialized equipment and complex processes in the prior art. The process of the present invention may be used to produce glass panels, bottles, glassware, lighting fixtures, plaques, trophies, decorative ornaments and any other glass articles producible by the methods disclosed in the prior art.
In the claimed glass printing process, a glass substrate or manufactured glass article is uniformly frosted on one surface by any conventional frosting process, such as abrasive blasting, chemical etching, or by mechanically abrading the surface. For example, in the abrasive blasting process, fine particles of grit impact the glass surface under pressure, causing an abrasion layer on one surface of the glass. The abrasion layer consists of sharp irregularities in the glass surface. The abrasion layer has the effect of refracting all light rays passing through the layer, giving the glass its frosted appearance. Upon completion of the abrasive blasting process, all or a selected portion of one side of a glass substrate is frosted or roughened, while the other side remains smooth.
In the next step, a silkscreen is created which carries the selected pattern. The silkscreen may be advantageously created using a computer program, a printer, and conventional silkscreen fabrication methods.
The prepared silkscreen or stencil is then mounted in a silkscreen press in alignment with the frosted glass substrate. A clear ink or epoxy in then deposited by screen printing, using a squeegee, onto the frosted surface of the glass substrate in the desired pattern carried by the silkscreen.
The clear ink or epoxy is selected to have an index or refraction which is approximately equal to the index of refraction of the glass substrate, and the ink is deposited to a depth which is at least equal to the depth of the abrasion layer or frosting. Upon completion of the printing operation, the glass substrate is removed from the printing stand and then cured. Alternatively, UV curable clear inks may be used. When the ink or epoxy has been cured, the glass printing process of the present invention is completed.
The resulting glass substrate or glass article has the same appearance as if it had been entirely frosted, except for the desired visible pattern that appears clear and transparent to light. In principle, the clear ink fills in the surface irregularities of the abrasion layer in the pattern carried by the silkscreen. Since the index of refraction of the clear ink is the approximate to the index of refraction of the glass substrate, the irregularities in the abrasion layer are essentially cancelled out or removed. Therefore, light passing though the printed regions of the glass substrate is [not] no longer diffused. The glass in the regions of the printed pattern appears clear, as if the frosting effect in those regions was never present.
In another aspect of the present invention, a process is claimed for producing selectively frosted glass articles. The glass article is first frosted on an entire predefined surface, and then the frosting effect is selectively removed by depositing clear ink on the glass article in a predetermined pattern.
In still another aspect of the present invention, a method is claimed for producing visible patterns on frosted glass. A visible pattern is selected and clear ink is deposited on the frosted glass in the selected pattern to cancel out or remove the frosting effect.
In still a further, the printing method is applied to transparent plastic articles and materials. The present invention may be effectively used with substrates made of plastics including acrylics and polycarbonates.
In an alternative embodiment, the printing process is applied to any type of specular reflective surface, such as polished marble. The polished surface is first roughened, and clear ink is then deposited by a silkscreen in a desired visual pattern. The clear ink restores the specular reflective appearance in the area of the printed visual pattern.